Poor gas mileage

So recently been getting terrible gas mileage , full tank an only 50 miles an it’s already at half a tank! An I baby this car, highway at 55mph. Not a lead foot .

New plugs,
New air filter
New fuel filter

Runs good, no black smoke. Curious to know if it’s a 02 sensor ?
I had a cel come on not long ago but when I got home and turned the car off and tried to read the codes it don’t give me a cel light or anything at all! Dazed and confused .

Have you tried any fuel additives? Those three seem to main the main culprits. I’ve used “Gumout Regane” with decent results. But it sounds like you’re getting ~8 mi/gal which — well there’s something REALLY wrong.

What about your tire pressure? Or brake calipers sticking?

Are you feeling any loss of power?

My tire pressure is at 35lbs in every tire , I don’t feel any loss in power significantly . I did check to see if the brakes were stuck but I jacked up the car and rolled the 4 wheels and seen if there was any grinding . Nothing at all or anything holding them back. One thing I’ve noticed is when I’m driving I’ll smell rotten eggs like crazy. I know that means catalytic converter . But could that be causing this whole issue?